A Democratic mayor’s warning to illegal immigrants of an incoming ICE raid in northern California may have led to a number of illegal immigrants with violent and sex-related convictions evading capture and deportation.

Oakland Mayor Libby Schaaf tweeted out an impending warning of the four-day raid last week, alerting targeted individuals to the imminent arrests, and infuriating Immigrations and Customs Enforcement (ICE) officials, who say that many more could have been caught if they hadn’t been warned.

The raid led to the arrest of 232 illegal immigrants in the San Francisco Bay Area, 180 of which ICE said “were either convicted criminals, had been issued a final order of removal and failed to depart the United States, or had been previously removed” from the country and had come back illegally.